Chemometric discrimination of airborne fibres: microplastics, regenerated cellulose and natural fibres

Interest in airborne microplastics has surged in the past decade, and a range of complementary tools are now used to characterize the different polymer found in samples. Most surveys, however, focus almost exclusively on synthetic fragments and fibres, overlooking the cellulosic fraction that often dominates particle counts. In this study, we measured the concentration of airborne particles in a range of indoor and outdoor settings and including densely populated areas, industrial zones, insular locations and natural reserve areas. We quantified both number- and mass-based concentrations of microplastics (MPs) and cellulosic fibres (CFs), with the latter outnumbering MPs by at least one order of magnitude. The average plastic-particle load was 0.024 MP/m (0.007-0.043 MP/m), whereas no MPs were detected in the natural reserve. MPs consisted mainly of polyethylene, acrylic and polypropylene, while polyester fibres predominated indoors. Because cellulosic materials can be either natural debris or anthropogenic fibres, we applied an advanced chemometric workflow, discriminant analysis coupled with Hotelling distances on mid-IR spectra, to distinguish cotton/linen textiles and regenerated cellulose (viscose, modal, Tencel) from plants, cutting ambiguous assignments by more than half. Roughly 50 % of all CFs were thus traced to textile sources. These results underline the importance of including CFs in airborne-plastic assessments and demonstrate that robust, yet widely accessible, μ-FTIR chemometric methods can deliver the resolution needed for accurate exposure and risk evaluations.